104 THE APODID^: PARTI 



pseudopodia without any apparent arrangement. 

 They contain the same minute olive green pigment 

 granules as the other pigment cells, which spread out 

 in great numbers over the subhypodermal connective 

 tissue layer throughout the body. This, however, is not 

 always the case ; some specimens had brown pigment 

 in large granules like those of the paired eyes. Some 

 of the pseudopodia penetrate a long way between the 

 retinal cells, and, at the surface of the organ where 

 there are no retinal cells, the pigment cells with their 

 long processes form together the external surface, 

 the whole structure having apparently no enclosing 

 membrane. The pigment cells, in fact, are nothing 

 more than a plexus of the ordinary pigment 

 cells which spread out irregularly throughout the 

 whole body, among the subhypodermal connective 

 tissue. 



In a well-preserved specimen, in which the pigment 

 did not happen to be very dense, the cells were seen to 

 send down processes towards the inner sensory ends 

 of the retinal cells. As these processes were regularly 

 arranged, and free from pigment, it was difficult at first 

 to decide whether they belonged to the retinal or to 

 the pigment cells. We mistook them at first for large 

 cilia belonging to the retinal cells. 



It will be seen from the drawings that the retinal 

 cells are not all of the same size. The lateral retinae 

 are composed of two distinct groups, an anterior group 

 of long narrow cells, and a posterior group of short 

 thicker cells. The ventral retina is composed solely 

 of large thick cells, and the dorsal of two groups of 



